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Nano Scale Creep and the Role of Defects

Published online by Cambridge University Press:  15 February 2011

S. A. Syed Asif  and
J. B. Pethica
S. A. Syed Asif
Affiliation:
Department of materials, University of Oxford, Parks road, Oxford OXI 3PH, UK.
J. B. Pethica
Affiliation:
Department of materials, University of Oxford, Parks road, Oxford OXI 3PH, UK.
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Abstract

The modulating force method in nanoindentation gives a direct measure of contact stiffness, and being insensitive to drift, allows the accurate observation of creep in small indents to be carried out over long time periods. We present results for a range of metals at room temperature. Strain rate indices similar to those for macroscopic creep are found. Reverse creep occurs for step unloading greater than about half the starting load. For electropolished tungsten, we find quite different behaviour before and after the sudden pop-in. Afterwards, creep is as in other metals, but beforehand, it is essentially zero. The slight changes of stiffness observed at the very smallest loads are due to diffusion of adsorbed surface films into the contact zone. Our results show that the dislocations nucleated and multiplied at pop-in provide the mechanism of creep.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 436: Symposium CC – Thin Films Stresses and Mechanical Properties VI , 1996 , 201
Copyright
Copyright © Materials Research Society 1997

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References

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